In most crude oil-containing deposits, the crude oil is forced out of the bore holes because of the pressure prevailing in the deposit. If the natural pressure is not sufficient for recovery of the oil, auxiliaries, such as water water/surfactant mixtures or gases, are pumped into the deposit in order to increase the pressure and/or to displace the crude oil from the oil-bearing layers.
U.S. Pat. No. 4,197,912 discloses a process for the extraction of crude oil from crude oil-containing deposits, in which organosiloxanes are dissolved or dispersed in hydrocarbons and this solution or dispersion is pumped into a bore hole to increase the yield. The handling of large amounts of hydrocarbons at the bore hole is hazardous owing to the low flash points and vapor pressures of the suitable hydrocarbons. In extensive deposits and low crude oil content of the deposits, the required amounts of hydrocarbon is not economical.
Processes have been described for the extraction of crude oil from crude oil-containing deposits in which an aqueous surfactant solution is injected into an injection well with the aim of forming a surfactant solution front in the deposit, which front pushes the crude oil in the direction of a production well. The mixture of water, surfactant and crude oil formed is extracted through a production well. Such a process is described in U.S. Pat. No. 4,296,812. The aqueous surfactant solution contains silicon dioxide/dialkylsiloxane in a concentration which is considerably lower than the concentration of the surfactants. A similar process is disclosed by U.S. Pat. No. 4,230,182, in which a surfactant-containing fluid is injected which comprises an aqueous surfactant-containing phase and a discontinuous hydrocarbon phase which contains up to 15% by weight of an off-soluble silicone compound.
However, in the above processes, the crude oil displacement efficiency is unsatisfactory. The crude oil displacement efficiency is based on the proportion of the crude oil displaced and extracted from the formation in comparison to the total amount of crude oil contained in the formation. In practice the crude off containing deposits comprise layers having different permeabilities for the aqueous surfactant solution, therefore, a surfactant solution front does not form. Instead, the surfactant solution flows rapidly to the production well through the more permeable layers leaving the crude oil in those layers that are less permeable to the surfactant. The crude oil content of the mixture of water, surfactant and crude oil extracted is frequently so low that further processing is no longer economical.